1. Field of the Invention
The present invention relates to a device that is useful for cutting rubberized fabrics, in particular rubber sheets of the type provided with reinforcing elements, the cut being in correspondence with one of the reinforcing elements, for the purpose of aiding the butt-end joining between the fabrics.
2. Prior Art
Continuous rubberized fabric tapes are already known that are provided with transversal metallic cords that are used, for example, in manufacturing carcasses for so-called radial tires. The continuous tapes are obtained by joining together rectangular lengths of said rubberized fabric, along the edges parallel to the direction of the metallic cords forming the reinforcing elements.
Two types of joining of rubberized fabrics are already known. The joining by overlapping, i.e. the superimpositioning of the sheet edges to be joined, and the butt-end joining simply by drawing closer and by butt-end joining the edges of the sheets to be joined.
The type of joining that is preferably chosen for the rubberized fabric, reinforced with metallic cords, is the butt-end joining method because, owing to the dimension of the metallic reinforcing cords, any joining by overlapping could present an intollerable thickening with the consequence of localized discontinuities characteristic of the so-formed continuous fabric tape.
From the prior techniques, apparatuses are already known that are capable of making provision for the butt-end joining. A first apparatus, that was described in U.S. Pat. No. 3,692,022 and U.S. Pat. No. 4,058,475, in the name of the same Applicant as for this patent application, discloses the butt-end joining, along the edges which are parallel to the metallic reinforcing cords of unvulcanized rubberized fabric lengths by means of clenching two edges of adjacent lengths in-between two flat comb-shaped jaws which draw together and penetrate in such a way as to completely join the edges, with local heating the edges of the fabric lengths for fostering the phenomena of adhesion and diffusion of the rubber compound in-between the two respective lengths. This system is very efficacious since the butt-end joining between the two lengths results is being decidedly reliable; however, it has the drawback of producing a thickening of the reinforcing cords adjacent to the two joined edges that could cause variations in the physical properties of the tape in correspondence with the joints that can not always be tolerated in the products obtained from such a tape.
A second apparatus, that obviates the above thickening phenomena in the reinforcing cords, is the one described in U.S. patent application No. 058231 filed June 4, 1987, also in the name of the same Applicant as for this patent application, which provides for the butt-end joining of two lengths of rubberized fabric still along the two edges parallel to the metallic reinforcing cords, by means of forcedly joining the edges in a progressive way through the action of two pairs of frusto-conical rollers that lie with one of ther generatrices against the lengths, for having the clenching between them, and by moving the rollers along the edges. In this way the butt-end joining is produced without any thickening of the reinforcing cords and so as to obviate the type of variations described above in the physical properties of the tape. However, success is not always to be had in obviating dis-uniformities in the rubber of the joining zone, due:
(a) to an excess of rubber material in-between the reinforcing cords immediately adjacent to the edges, that causes the formation of a bulge, or a weld, in correspondence of the joining; and
(b) to breaks in the continuity, or burrs in the cut-off rubber edges that cause a thinning-out, or even, spaces left open in the joined zone.
In the worst case, the disuniformity could include both of the defects mentioned above i.e. localized bulges alternated with thinnings, or gaps, in the joined zone.